x86 idle: deprecate "no-hlt" cmdline param

We'd rather that modern machines not check if HLT works on
every entry into idle, for the benefit of machines that had
marginal electricals 15-years ago.  If those machines are still running
the upstream kernel, they can use "idle=poll".  The only difference
will be that they'll now invoke HLT in machine_hlt().

cc: x86@kernel.org # .39.x
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index fc505c1b476280286b7459d39a3698f5e60358f9..f1b0eb02aa1dd12d9ceaa43e8f8dbe3a29c2d39c 100644 (file)
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -24,6 +24,17 @@ Who: Len Brown <len.brown@intel.com>
 
 ----------------------------
 
+What:  x86_32 "no-hlt" cmdline param
+When:  2012
+Why:   remove a branch from idle path, simplify code used by everybody.
+       This option disabled the use of HLT in idle and machine_halt()
+       for hardware that was flakey 15-years ago.  Today we have
+       "idle=poll" that removed HLT from idle, and so if such a machine
+       is still running the upstream kernel, "idle=poll" is likely sufficient.
+Who:   Len Brown <len.brown@intel.com>
+
+----------------------------
+
 What:  PRISM54
 When:  2.6.34
 

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index c39576cb3018507f2d359521741c1764778b68f7..525514cf33c308aff9d29e66d274207e7f4e8308 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -19,6 +19,7 @@
 
 static int __init no_halt(char *s)
 {
+       WARN_ONCE(1, "\"no-hlt\" is deprecated, please use \"idle=poll\"\n");
        boot_cpu_data.hlt_works_ok = 0;
        return 1;
 }